On the one hand, the invention relates to a device for exerting a return force on at least one harness element of the harness of a Jacquard weaving machine, comprising at least one return spring provided with means of attachment in order to attach the return spring to retaining means immovably provided. On the other hand, the invention relates to a device for immovably installing the retaining means of one or several return springs of a jacquard weaving machine, the device being provided with at least two fixed installing elements for installing the retaining means.
In a Jacquard machine, one or several return springs are applied at the bottom of the harness, in order to tighten the Jacquard heddle, the harness cord, the tackles, the tackle cords and the two complementary hooks, so that the noses of the hooks will be kept permanently in touch with the blades or, in case of a selection, will certainly stay on the suspension means. The spring force of these return springs at the bottom of the harness will compensate the tension of the pile warp yarn, the inertia and the friction of the heddles, of the harness cord, of the tackles with their cords and of the hooks. Most of the time, the return springs are connected to a fastening piece, which is provided with a hook, by which each return spring is attached to a board, called flat bar, which is built-in in the machine. This fastening piece may be screwed onto the return spring, which is or is not provided with damping means (=element of synthetic material situated in the return spring in order to prevent the extremity of the return spring from absorbing the heaviest chocks). The hook is usually a metal hook, which is hooked onto the flat bar.
This design has the disadvantage, that the return springs which have been installed on the flat bar next to one another, are not self-gripping what causes the return springs to loose their exact positions, each time the harness is released and because of this the position of the return springs in the warp direction becomes uncertain and no longer in correspondence with the pitch of the cumber board. Because of this, friction in the harness will increase or it may lead to a hooking together of the springs in case of major dimensional deviations. When the foremost return springs are shifting forward too far they may collide with the reed. The shed also may change in consequence of the position lost in the warp direction, because of which the rapier may collide with the shed.
In order to better secure the position in the warp direction designs are known where the return spring is glued to the flat bars.
This has the disadvantage that replacement on site becomes very difficult.
Another design consists in bringing in spacers on the flat bars between the various return springs and then tightening the whole.
However this design has the disadvantage that a large variety of spacers are required with different thicknesses requiring quite some work for installation. Here, replacements on site are also labor-intensive.
Another solution to be applied is overmoulding the flat bars. During the production process of the hooks, the flat bars are inserted, so that the hooks are overmoulded directly at the distances required.
The disadvantage of this method is that a large number of parts have to be overmoulded simultaneously. Besides, this production method is hardly flexible and replacement on site becomes very difficult.